I have faced with the following problem:
I'm building localized version of some NB-based tool. 
JavaHelp files is a part of that localization. 
I build separate jars with javahelp files.



Then the scenario is:
- $ ./my-tool --userdir ud
- Press F1 => en help is fine
- Exit tool

- $ ./my-tool --userdir ud --locale ja
- Press F1 => NPE
- Exit tool

- $ ./my-tool --userdir ud --locale ja -J-Dnetbeans.cache.manifests=false
- Press F1 => ja help is fine
- Exit tool

While investigation of the problem I have found that JavaHelp throws MissingRecourceException in case of a second start (above). And this is because classloader (NB's) tells so. In turn this happens because userdir already exists at the time of NB start and there is NO mention about ja JavaHelp-related jars there. But as all-manifest.dat exists it is not get updated... (see NbInstaller.java:1199, and as a result no call to saveManifestCache())

I see that there are mechanisms that work good for changed resource files (updating all-resources.dat). But my jars with translated JavaHelp are not considered as resources... and don't trigger all-manifest.dat refresh.

Seems like unserved usecase.. 

A workaround is either remove var/cache/all-manifest.dat or start with -J-Dnetbeans.cache.manifests=false...